1. Field of the Invention
The present invention relates to a method for the deposition and fixing of a thin metal wire on the surface of a thermoplastic film of a laminated glazing, in which the thermoplastic film is kept by vacuum on the surface of a cylindrical drum which is rotated, and the metal wire is deposited in continuous manner on the film, as a result of the application of a linear advance movement to the wire deposition apparatus on a guide positioned parallel to the drum axis and with the aid of a wire deposition apparatus having a heated crimping tool, a wire supply reel and means for moving the wire from the wire supply reel below the heated crimping tool. It also relates to an apparatus for performing the method and to a thermoplastic film obtained from said method.
2. Discussion of the Background
A method of the aforementioned type is known from DE 4 201 620 A1. In this known method, the wire deposition apparatus is moved parallel to the drum axis by means of a screw drive while the drum rotates. As a result of a regular advance of the wire deposition apparatus along the axis, the wire is helically deposited on the surface of the drum and forms wire segments extending rectilinearly in a parallel arrangement on the film. The crimping tool is in this case constituted by a heated pressure roller. An electromagnetic brake is coupled to the supply reel to keep the wire under a predetermined tension.
Another known method is disclosed in EP 443 691 A1. In this case, prior to helical deposition, the wire is deformed by two meshing toothed wheels, so that it is deposited on the thermoplastic film in an undulating manner.
The known methods are used on a large scale for the production of electrically heatable, laminated safety glazings. In this case, collector conductors in the form of tinned copper foil strips are fixed to the thermoplastic film along two opposite edges of said film. Following the helical deposition of the metal wire, the latter is connected to the collector conductors by another tinned copper foil strip deposited on the lower copper foil strip, and the two copper foil strips are brazed to one another with inclusion of the wires. The wires are then cut into sections outside the collector conductors. The film provided with the wire segments is then removed from the drum for incorporation in the laminated glazing.
The heated laminated safety glazings are used both in buildings and in vehicles. In most cases, particularly in the case of rectangular glazings, the arrangement of the heating wires in rectilinear manner, such as is obtained with the aid of the aforementioned methods, is desired. But it has also been applied to non-rectangular glazing shapes, especially in the case of the heatable car rear windows.